Computer system interrupts are a computer system microprocessor's means of communicating with other elements that make up a computer system. In general, computer system interrupts have been passed directly to the computer system microprocessor through the interrupt terminals of the microprocessor. The interrupt causes the microprocessor to suspend its current operations, save the status of its work, and transfer control to a special routine (known as an interrupt handler) that causes a particular set of instruction to be carried out. Interrupts have been generated for many reasons, ranging from normal to highly abnormal. These can include service requests from various hardware devices, errors in processing, program attempts to cause the computer system to do functions it is not capable of performing, and imminent failure of some vital component.
Nevertheless, only a limited number of hardwire interrupts--interrupts physically connected to a microprocessor interrupt terminal through control circuitry--could be accommodated by a processor, or they could not be implemented due to the complexity of a computer system's architecture.
Accordingly, a need exits for emulating a hardwired interrupt to achieve the same computer system effect on the system hardware, without having a hardwired interrupt connection to a microprocessor interrupt terminal.